Cytogenetically negative, linkage positive "fragile X" syndrome.


We investigated the family of a 3-year-old boy with manifestations of the Martin-Bell syndrome (MBS). His 17-year-old cousin had classic manifestations of MBS and was fragile X [fra(X)] positive. The 3-year-old boy was fra(X) negative. Linkage analysis with probes flanking the fra(X) region indicated that these cousins had the same X chromosome inherited from a normal grandfather. The DNA and cytogenetic analyses suggest that limitations in the ability to detect the fra(X) mutation cytogenetically may be responsible for fra(X)-negative MBS; or, alternatively, that a crossover occurred between a locus determining the MBS phenotype and one determining fra(X) expression.

Cite this paper

@article{Brooks1991CytogeneticallyNL, title={Cytogenetically negative, linkage positive "fragile X" syndrome.}, author={Susan Sklower Brooks and Ira L Cohen and Carlo Ferrando and Edmund C Jenkins and William Brown and Carl Dobkin}, journal={American journal of medical genetics}, year={1991}, volume={38 2-3}, pages={370-3} }